Tipifarnib (Zarnestra) is a farnesyltransferase inhibitor with an IC50 of 0.6 nM. It is a nonpeptidomimetic quinolinone with potential antineoplastic activity. It binds to and inhibits the enzyme farnesyl protein transferase, an enzyme involved in protein processing (farnesylation) for signal transduction. By inhibiting the farnesylation of proteins, it prevents the activation of Ras oncogenes, inhibits cell growth, induces apoptosis, and inhibits angiogenesis.